It is a tossup.
If we leave there, it will be like we started some stuff that we couldn't finish, and Iraq may collapse again.
If we stay, there will likely be more fighting yet, and it will still take time, and again, it still looks bad.
I also feel that the oil argument is not viable, it is counterintuitive to me. Any 'benefit' from it is lost due to expenditure and a hurting economy, for one. Second, it is not beneficial to the oil market, it is actually a hindrance. It would have been better off leaving Iraq alone and gaining it through diplomacy... if this move was for oil, it was a very stupid move, almost like "shooting yourself in the foot". It did drive up oil prices, but that has diminishing returns, and eventually has a negative effect rather than a positive one... if the oil is -too- expensive, you actually will lose more money than a point on the curve where it would be cheaper (because people would be insane to pay for it after a certain point, therefore sale volume drops, along with profit).